1. Field of the Invention
The present invention relates generally to blender apparatus, and more particularly to a blender apparatus including an automatic level control device.
2. Description of the Prior Art
Many activities conducted in connection with the servicing of oil wells involve the blending of one or more solid particulate materials with a liquid which is to be pumped down into a well.
A relatively recent development by the assignee of the present invention is the constant level additive mixing system disclosed in U. S. Pat. No. 4,490,047 to Stegemoeller et al. The Stegemoeller et al. '047 system provides a blender tub which is resiliently supported from a base by a torsion bar extending through the tub. As the fluid level in the tub changes the tub resiliently moves relative to the base. This movement is transmitted to a control valve which then responds by directing more or less fluid to the blender tub, thus controlling the fluid level within the tub.
The purpose of this system provided in the Stegemoeller et al. '047 patent is to provide a blender typically of relatively low capacity which does not need to be constantly monitored by a human operator.
A number of problems have been encountered with the system of the Stegemoeller et al. '047 patent.
For one thing, the torsion bar utilized to suspend the blender tub in the '047 patent extends through the body of the blender tub itself thus interfering with the flow of fluid in the blender tub and preventing the use of some forms of mechanical agitation which would extend down to the bottom of the blender tub.
Furthermore, the blender tub of the '047 patent tilts to one side as the fluid level therein is increased, and has a rather substantial movement on the order of eight to twelve inches between its full and empty positions. This, too, is not ideal.